Autogenerate random username?

Hi,
I am using emailaddress to login, to make it easy to my users. They only use frontend. So they don't need the username. But in registration they have to create a username (They cannot understand why).
My question (or proposal is) is there a possibility to autogenerate random username, for example a part of name and number or something like that?

If username is removed from registration then it'll add the Name as the username. If Username and Name are both removed from registration then it'll add Email as Username and Name. I suppose you could use CB Auto Actions with an after registration trigger to alter the username to whatever you want while keeping Email and Name on registration.